The Big Idea: How a liquid biopsy changes cancer treatment

Alex Sarmiento, 77, has good reason to feel optimistic about his future. Three years ago, Alex was diagnosed with prostate cancer and the disease had spread to other parts of his body.

"I asked Dr. Nanus, 'Should I retire?" said Dr. Ida Tiongco, Alex's wife. "Because if your husband is dying you want to enjoy the last years of your life together."

At first Alex's condition with treatment remained stable. But in April, after a trip to visit family in the Philippines, his health rapidly declined.

"I was weak and exhausted," he said. "I thought it was jet lag."

Ida said her husband was twice put in the hospital and given debilitating rounds of chemotherapy.

"When you have cancer there is really no relief," she said.

Instead of getting better, Alex was getting weaker.

New York Presbyterian's Dr. David Nanus, chief of hematology and medical oncology, decided to give Alex a "liquid biopsy." This diagnostic test with the help of technology is being used in new innovative ways.

Dr. Scott Tagawa is an oncologist at New York Presbyterian.

"If someone develops advanced cancer... metastatic cancer – that is, individual cells from the tumor breaking off and landing somewhere else," Dr. Tagawa said. "As those cells travel around in the blood we can capture them in a test tube. We could then take those individual cells from the test tube and analyze them."

The test is relatively non-invasive. In the past, in order to get tumor cells from a patient, a doctor had to do surgery or biopsy. Now a nurse draws blood from the arm, like what happens in a routine blood test.

The blood sample is taken to a laboratory in the hospital. The sample is put into a machine called a CellCelector. Using the CellCelector, the lab technician can isolate cancer cells from the healthy blood cells. Images of the cancerous cells are then projected on computer screen to be studied by a doctor.

The pictures can reveal what kind of tumor it is, the DNA of the tumor, and it if the cancerous tumor is becoming resistant to a drug.

The results of the liquid biopsy help doctors customize a treatment for the patient because it can determine the type of tumor a patient has and what medicine will work best in treating it.

Dr. Tagawa said it also allows him to figure out why a patient's tumor is becoming more resistant and get ahead of that.

Some doctors say the liquid biopsy has revolutionized oncology. The results allow doctors to track the progression of a disease in real time. You could have liquid biopsy every day. Essentially removing the guess work allowing doctors to prescribe the right treatment.

Dr. Nanus said that within a week the results from Alex's liquid biopsy showed that he had a certain kind of mutation. So Dr. Nanus was able to quickly make a treatment decision and prescribe the right drug.

Just a few months into his new treatment, Alex's health dramatically improved.